Spiral antenna with overlapping turns

ABSTRACT

An antenna of the type that radiates a circularly polarized electromagnetic energy field is constructed with one of an included pair of transversely overlapping double-wound spiral conductors secured to a different one of substantially parallel opposite surfaces of a dielectric support means. The improved broad band antenna radiates energy in the range of approximately 2 to 17 GHZ without radiation pattern degradation at higher peak power values in comparison to conventional circularly polarizing antennas.

United States Patent Stropki [451 Apr. 11, 1972 [54] SPIRAL ANTENNA WITH[56] References Cited OVERLAPPING TURNS UNITED STATES PATENTS [72] GammaOhm 3,509,465 4/1970 Andre et a]. ..343/895 [73] Assignee: NorthAmerican Rockwell Corporation, El

Segundo, Cahf- Primary Examiner-Eli Lieberman [22] Filed; May 25, 1971Attorney-L. Lee Humphries and Daniel H. Dunbar pp 146,819 57 ABSTRACTRelated U.S. Application Data An antenna of the type that radiates acircnlarly polarized [63] continuatiomimpan Ofser. No 856,283 Sept. 1969electromagnetic energy field is constructed with one of an meluded pairof transversely overlapping double-wound spiral abandoned.

. conductors secured to a different one of substantially parallel 52 us.Cl ..343/895 PP Surfaces ofa dielectric support means- The impmved 5 CL01 1 3 broad band antenna radiates energy in the range of approxi- 58Field of Search ..343/s95, 908 mately 2 to 17 6111 without radiationPattern degradation at higher peak power values in comparison toconventional circularly polarizing antennas.

2 Claims, 6 Drawing Figures PATENTEDAPR I 1 I912 SHEET 1 BF 2 IN VENTOR.

GEORGE T. STRQPKI ATTORNEY PATENTED APR 1 1 I912 SHEET 2 BF 2 INVENTOR.

GEORGE T. STROPKI ATTORNEY SPIRAL ANTENNA WITH OVERLAPPING TURNSCROSS-REFERENCES This is a continuation-in-part application ofapplication for U.S. Pat. Ser. No. 856,283, filed Sept. 9, 1969 but nowabandoned in favor of this application.

SUMMARY OF THE INVENTICN The antenna of this invention is constructedwith a dielectric support member having essentially parallel oppositesurfaces, such member normally being formed from a polymerized organicresin having reinforcing glass fibers or from a comparable dielectriccomposition. A pair of spiral metallic conductors is preferablyconfigured on and adhered to the dielectric support member byconventional etched or printed circuit manufacturing processing or thelike, each conductor being supported entirely on a different one of theparallel opposite support member surfaces. The individual conductors areeach normally electrically energized from a center feed terminal by aconventional balun or coaxial feed assembly; such conductors are alsonormally either openended or sometimes terminated at a perimeterterminal to a conventional matching circuit. The individual conductorsalso are closely spaced in their transverse projected relationshiprelative to each other to provide a reduced axial ratio antennaoperating characteristic, are energized by high frequency (2 to 17 GH,)alternating electrical currents that amplitude-wise are continuously 180out of phase with respect to each other SUMMARY OF THE DRAWINGS FIG. 1is a sectional view of a flat double-wound spiral antenna having thebiplanar conductorfeatures ofthis invention;

FIGS. 2 and 3 are plan views of the antenna of FIG. I showing theconductor configurations at the opposite surfaces of the antennadielectric support means;

FIG. 4 is a sectional view of a flat double-wound spiral antenna havingthe features of this invention but with individual conductors of varyingwidth; and

FIGS. 5 and 6 are plan views of the antenna of FIG. 4 showing theconductor configurations at the opposite surfaces of the antennadielectric support means.

DETAILED DESCRIPTION FIG. 1 illustrates a section through a circularlypolarizing antenna 10 having flat dielectric support member 11 providedat its opposite planar surfaces 12 and 13 with metallic conductorelements 14 and 15, respectively. In many applications, dielectricsupport means 11 may be a polymerized organic resin such aspolytetrafluoroethylene reinforced with glass fibers or a similarcomposite with other organic resin material such as a polyphenyleneoxide or an epoxy.

Conductors 14 and 15 are configured and adhered to the opposite surfaces12 and 13 of dielectric support means 11 in a conventional manner as bystate-of-the-art antenna design and etched or printed circuit boardmanufacturing techniques. As shown in FIGS. 2 and 3, conductors 14 and15 specifically may each have an equiangular spiral configurationwherein the conductor is also substantially of uniform width from nearits centered feed terminal 16 (or 17) to near its respective perimeterterminal 18 (or 19). In other applications such conductors may beArchimedian spirals, for example, or may have square spiralconfigurations rather than essentially circular spiral configurations.The invention also has application to configurations for dielectricsupport member 11 other than the essentially flat, plate-like orsheet-like dielectric support member shape of the drawings. Forinstance, the invention has application to hollow, conically orpyramidally shaped dielectric base means since it is only critical thateach one of the paired conductors be provided substantially on adifferent one of opposed, essentially parallel support surfaces and intransversely overlapping relationship relative to each other. Suchinvention in instances permits an increase in peak power handlingcapability from approximately 500 watts to as much as nearly 5,000 wattsfor the bisurface transversely overlapping conductor arrangement overthe single surface conventional circular polarizing antenna constructionwith equivalent double-wound conductor widths, spacings, and lengths.The improvement is effected without significant radiation patterndegradation and without antenna radiation voltage breakdown.

The antenna embodiment 20 of FIGS. 4 through 6 illustrates the requiredconductor transverse overlap relationship that is effective to obtain asignificant increase in peak power handling capability in connectionwith the instant invention. Such is accomplished by transverselyoverlapping the widths of the individual conductors 24 and 25 secured tosupport surfaces 22 and 23 of dielectric member 21 in the regions fromfeed terminals 26, 27 to perimeter terminals 28, 29 in the generalmanner shown in FIGS. 5 and 6. As shown therein, conductors 24 and 25each have a maximum width in a region of the conductor length nominallyassociated with the center frequency of the desired antenna operatingband-width and the maximum width of conductor 24 considerably overlapsthe edges of the transverse projected widths of the adjacent turns ofconductor 25 and vice versa. In fact, except for a relatively narrowseparation between adjacent edges of a conductor in a radial direction,each conductor may approach being sheet-like in its basic configuration.

This relationship is readily facilitated by the fact that the individualconductors are secured to the opposite support surfaces 22 and 23 ofdielectric base means 21 and results in a significantly reducedimpedance value for the antenna assembly, other constructioncharacteristics being equal. In one specified embodiment of a circularlypolarizing antenna with a square spiral configuration, the assemblyimpedance was reduced from ohms to approximately 50 to 60 ohms by use ofthe varying width conductors on opposite surfaces of the dielectricbase. In terms of increased peak power, for a given input power levelthe peak power can be further increased approximately 40 percent by thetransversely overlapping conductor feature in the bisurface antennaarrangement.

The instant invention is not limited in its application to antennaconstructions utilizing either uniform width or variable widthconductors. More specifically, the transversely overlapping conductorrelationship necessary to obtain a significant reduction in antennaimpedance may also be developed with other conductor forms such as theslow wave antenna conductors shown in U.S. Pat. Nos. 3,454,95l and3,465,346.

By incorporating the features of this invention in a circularlypolarizing antenna it is possible to obtain antenna impedances to as lowas approximately 50 ohms. The use of such transversely overlappingconductor features in an antenna also permits the use of simple coaxialfieed devices rather than balun devices, thereby contributing further tothe improved power handling capacity of the invention. It should benoted that the opposed conductors are fed. with radio frequency signalsthat are out of phase with respect to each other. At the radiation bandthe fields radiated from the transversely overlapping conductor sectionsare coupled and reinforce each other.

I claim: I

1. In an antenna of the type which radiates a circularly polarizedelectromagnetic energy field, in combination:

ments being adhered substantially entirely to a different one of saiddielectric support means exterior opposed essentially parallel supportsurface areas, and also being positioned in substantial transverselyoverlapping relationship relative to each other in the principalradiating regions of the element.

2. The invention defined in claim 1, wherein said multipletum spiralconductor elements are each varied in width in their length from aregion near the connected one of said feed terminals to a region near anassociated perimeter terminal.

1. In an antenna of the type which radiates a circularly polarizedelectromagnetic energy field, in combination: a. Dielectric supportmeans having exterior opposed essentially parallel support surfaceareas, b. A pair of feed terminals that each conduct a different one oftwo equal-amplitude electrical currents continuously 180* out of phasewith respect to each other, and c. A pair of multiple-turn spiralconductor elements that are each electrically connected to a differentone of said feed terminals and that together radiate a circularlypolarized electromagnetic energy field, each one of said pair ofmultiple-turn spiral conductor elements being adhered substantiallyentirely to a different one of said dielectric support means exterioropposed essentially parallel support surface areas, and also beingpositioned in substantial transversely overlapping relationship relativeto each other in the principal radiating regions of the element.
 2. Theinvention defined in claim 1, wherein said multiple-turn spiralconductor elements are each varied in width in their length from aregion near the connected one of said feed terminals to a region near anassociated perimeter terminal.